Doorknobs May Be 'Reservoirs' for MRSA

Sept. 19, 2011 (Chicago) -- If a member of your household has a drug-resistant staph infection, be aware that doorknobs, light switches, and other seemingly harmless items may serve as reservoirs for the bacteria to multiply and spread.

People with MRSA (methicillin-resistant Staphylococcus aureus) who live in homes where such common items test positive for the same strain of MRSA are about five times more likely to spread the bacteria to another household member, a study of nearly 300 homes suggests.

Staph, including MRSA, is a common bug that lives on the skin or in the noses of about 40% of people without causing harm, says researcher Justin Knox, MPH, a PhD candidate in the department of epidemiology at Columbia University in New York City.

But previous research by the same group suggests that contamination of household items is associated with an increased risk of recurrent MRSA infections, Knox tells WebMD. "Environment appears to play a role in [MRSA spread]."

The study also showed that having a child age 5 or younger or having a pet in the home doubles the risk of transmitting staph to another household member.

Knox presented the findings here at the 51st Interscience Conference on Antimicrobial Agents and Chemotherapy.

MRSA on the Rise

A 2005 study showed that the annual rate of community-acquired MRSA infection -- cases occurring in people with no recent hospital or nursing home stays -- ranged from 18 cases per 100,000 people in Baltimore to 26 cases per 100,000 people in Atlanta.

Since then, there has been a dramatic increase in cases, and studies suggest that community-acquired infections are often contained within households, according to Knox's colleague, Anne-Catrin Uhlemann, MD, of Columbia University.

However, the source of these infections has been unclear.

So Knox and colleagues compared the households of 146 people who came to the hospital to be treated for community-acquired MRSA infections to a comparison group of households of 145 dental clinic patients.

Patients completed a questionnaire about themselves and household members. Also, nasal swabs were collected from consenting household members, and household items were swabbed. Swabs were cultured for staph bacteria.

Among the findings:

58% of household members of people with MRSA infections tested positive for staph vs. 37% of those in the other homes.

Identical MRSA strains were found among two or more members of the household in 38% of "hospital-treated" households vs. 18% of the comparison households.

Common household items tested positive for the same strain of MRSA as the patient in half of "hospital-treated" households vs. less than one-third of comparison households.

Minimizing Your Risk of MRSA

So what should you do to minimize the risk of MRSA spreading in your household?

Practice good hand washing techniques, says Catherine Bennett, PhD, head of the School of Health and Social Development at the Deakin University Australia in Burwood, Victoria, Australia. She moderated the session at which the findings were presented.

Whether to clean doorknobs, counters, and other potential sources of infection with bleach or antimicrobial agents is tricky, Bennett says. "You don't want to encourage resistance. So use them in moderation."

If you have a young child, make sure he or she follows these recommendations.

These findings were presented at a medical conference. They should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.